Dairy Science and Food Technology

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Milk provides the newborn (neonate) with nutrients and an array of antimicrobial factors.  These are believed to help protect neonates from infection until their own immune system has developed.This section of the dairy science website reviews the properties and potential nutritional and industrial significance of the major antimicrobial systems of milk, with particular reference to the lactoperoxidase system.

As more pressure is applied to reducing production costs, attention is increasingly being given to maximising the yield of high moisture cheeses including Cottage cheese. While yield is important, cheese quality must also be considered whenever attempts are being made to improve or optimise yield.

Considerable academic and commercial research has been devoted to optimising the yield of un-dressed or un-creamed Cottage cheese. There is now a significant volume of academic research freely available or available at low cost (On Line databases may require payment by credit card to access some journal articles); this is easy to access. Commercial information of varying quality, some of it surpassing what is available in the research literature, is also available but this is difficult to access.

Case study

This section contains the results of an actual investigation of an apparent reduction in the yield of Cheddar cheese made in October of year X compared with the same month a year previously. 

Five  vats of cheese were manufactured in the factory and the milk and cheese were subject to chemical analysis. The samples were analysed at a reputable laboratory.

The following data (Table 1) for milk, cheese and yield (adjusted per 100 kg of milk) were obtained.

This section of the Dairy Science and Food Technology website provides an outline of how the commercial 'cheese yield problem' outlined earlier might be approached and how yield and cheese component retention can be analysed and presented. This is achieved using a unique on-line calculator that is shown in the cheese yield spreadsheet.

Data from 5 vats of commercial Cheddar production are summarised in the cheese yield spreadsheet. The data set are different to the problem given previously. The cheese and milk data were obtained from one day's production. The casein:fat ratio of milk in each vat has been calculated and for information casein as a percentage of protein has been presented.

There is increasing interest in farmhouse cheese making in the UK and Ireland and Jongia (UK) Ltd., a supplier of equipment and ingredients to the UK and Irish dairy industry, offers study tours to German dairies. These study tours offer existing and potential new businesses an opportunity to see equipment in action and to discuss cheese production and marketing with farmhouse producers.

The study tours are offered as intensive one or two day trip, depending on flights and and are planned to be low cost.

Study tours take place in the spring and autumn each year.  Participants can select from 3- routes, each with a different accent for a different market. Many cheese makers have joined all of the trips, even a few coming twice! Participants have included seasoned cheese makers, novices and hobbyists.

Routes

Berlin area, 3 - 4 dairies, with the accent on fresh products, like drinking milk, yoghurt, curd cheese (quark) and soft cheese. Two of the dairies are organic (one bio-dynamic) and one is goat milk dairy. Depending on flights we can execute this as a day trip

Westpahlia (Dortmund area), 5 or more dairies. The accent is on Gouda/Edam type cheese and curd cheese (quark).

Bavaria/Austria border. 4 dairies with the accent on soft cheese and mountain cheese. The latter is an Edam type process with a red smear coating.

Our participants are always very enthusiastic after the trips, having not only seen new ways to solve problems they might have, but also having made new contacts and friends. All have indicated that the interactions with the other participants were an important part of each study tour.

Examples of  technology and developments seen on study tours

The Westphalia trip visits exclusively cheese makers who are also farmers and run farm shops as well, while a few also run restaurants. These farmers are now entrepreneurs of the first degree and are eager to share their experience with us. Images of a dairy shop are given in plates 1-3 below.

 

 Exterior of farm dairy shop at Thomashof in Burscheid

 

The questions below have been designed to test knowledge and understanding of cheese science and technology. They are based on an E-book that I will eventually incorporate into the site. In the meantime 'browsers' can test their knowledge and understanding of cheese technology by attempting the questions below. A link to most of the answers is also given at the end of the question section. 

Cheese science and technology questions.

Chemical differences between cheeses

What makes one cheese e.g. Cheddar different from another e.g. Gouda or Emmental?

Can you explain why Gouda cheese is different than Cheshire or what makes Emmental different than Cheddar cheese? What about other cheeses too? And, we need an answer that is more sophisticated that saying the level of starter addition is different!

The need for cheese grading

This article explores a model using simple chemical and physiochemical components that can be used to predict the quality of Cheddar cheese and whether a batch of cheese is suitable or extended maturation to yield a high value mature cheese. The model can be freely evaluated using an On Line calculator.

Assessment of cheese quality is essential in order to determine if the cheese conforms to legal standards, meets the requirements of the buyer and ultimately the customer and to grade the cheese for payment. A cheese may meet all legal and safety requirements but have appearance, taste, flavour and or texture defects that make it unpalatable or only suitable as an ingredient in e.g. sauces. Because cheeses like Cheddar require extended maturation in some cases for as long as 18 months or more to give extra mature high value cheese, assessment of quality through a grading scheme is used to exclude cheeses with defects. Storage is expensive and companies cannot afford to waste money storing inferior quality cheeses.

The traditional method of assessing cheese quality combines visual, organoleptic and physical assessment by a cheese grader and is called grading. Until relatively recently the suitability of cheese for end consumer use was judged almost entirely on flavour and texture assessments by commercial cheese graders. To assess the cheese, the cheese grader uses a cheese iron to extract a core of cheese. The grader visually examines the outside of the core, and breaks the core to examine a cross section of the core. The hardness or softness of the core and its resistance to deformation are also determined. The 'smell' of the sample core, immediately on withdrawal from the cheese and after working (squeezing a portion of the core into a malleable mass), also provides the grader with information on aroma. 

The author coring cheese at a cheese show

The author coring a cheese at a cheese show in Dublin.


These typically form the basis of traditional approaches to cheese grading.

This page provides access to an interactive spreadsheet in which data for the chemical composition of milk and cheese and actual yields can be recorded. The software will then calculate theoretical yield, process efficiency, key compositional criteria and provide a basic statistical analysis of the results. Real data have been provided and these can be replaced with test data to use the spreadsheet.

This software could be used with the cheese yield problem provided along with the overview of how the problem might be investigated to teach the principles of process control in cheese manufacture.

 

Go to interactive spreadsheet.

Whole milk powders with a range of fat concentrations are available commercially. The dairy technologist may be required to standardise raw milk to a particular fat concentration to enable the production of powder to a specified fat concentration to be produced.

A calculator for determining the fat concentration required in the raw milk to produce a powder of a specified fat concentration
can be accessed here.

This is the access page to the free molarity calculators designed by Dr Michael Mullan. It is not unusual for students and others to miscalculate the volumes of solutions or the weight of compounds required to produce solutions. The molarity calculators accessed here should enable students and others to check their calculations.

The calculator below is based on a model developed by Giles and Lawrence (1973) to predict the grade value of Cheddar cheese. Instructions on how to use the calculator are given below. Note that the pH and other values should be obtained from 24-hour old cheese.

Ice Cream Mix Calculator

The objective in calculating ice cream mixes is to turn a formula into a recipe based on the intended ingredients and the mass or volume of mix required.  The recipe is then processed to obtain ice cream for distribution and sale.  In the UK and in North America the formula is given as percentages of fat, milk solids-not-fat (MSNF), sugar, stabilisers-(stabilizers in the US) and emulsifiers. Since several ingredients may be available to supply these components e.g. MSNF available ingredients are selected on the basis of quality and cost.

Because the concentration of fat and protein in milk vary with season, and other well documented factors, it is necessary to adjust the composition of milk for use in the manufacture of cheese and other dairy products. This process, called milk standardisation (standardization in the US) is designed to ensure that product quality is maintained at a consistent level throughout the year. This area will be dealt with in more detail elsewhere in this website.

Increasingly standardisation is being done automatically using on line instrumentation. In small dairies this is still done 'manually' including calculating the volumes (or weights) of skim milk and whole milk required to produce a particular quantity of milk of a defined fat concentration.

One of the simplest methods of routinely adjusting the fat concentration of milk for cheese, ice cream or whole milk powder manufacture is to use the Pearson Square or Rectangle. This method may also be called Pearson's Square or Pearson's Rectangle. This is a simplified method for solving a two variable simultaneous equation. While it is being used here with milk it is is a tool that can be used to help processors calculate the amounts of two components that need to be mixed together to give a final known concentration. For example, it can be used to calculate the amounts of fruit juice and sugar syrup to be mixed to make a fruit squash or fruit pulp and sugar to make a jam. It is also used in mixing rations for animal feeding and in the meat industry to produce meat products e.g. sausages to a particular fat content. Wines and other alcoholic beverages are also blended to give products of a specified alcohol concentration.New gif Microsoft Excel spreadsheets for undertaking these calculations can be downloaded.New gif

This tool can only be used for blending two components. When more than two components are involved, more complex mass balance equations have to be used. The first step in using this method is to draw a rectangle. At the centre of the rectangle write the concentration of fat required in the cheese milk. At the upper left hand side write the % fat concentration of the milk; the most concentrated fat source used. At the bottom left hand corner place the fat concentration of the skim-milk used. On the top right hand side write 'parts milk' and on the bottom left hand side write 'parts skim'.

The 'parts milk or skim' are obtained by subtracting the lowest value number, working diagonally, from either the desired final fat concentration in the case of milk or by subtracting the value for final fat concentration from the concentration of fat in the milk.

This process gives the proportions of milk and skim that must be mixed together to give the desired fat concentration. Knowing the weight or volume of the final mix, the actual quantities of milk and skim required can be obtained by a simple proportional calculation. Note this method can also be used to standardise protein, SNF and/or casein in milk.

Browsers can test their understanding of this basic calculation by using the calculator below. More information on Milk Standardisation is available in the Answers to cheese science and technology self assessment section.

Click here to use the calculator


How to cite this article

Mullan, W.M.A. (2006). [On-line]. Available from: https://www.dairyscience.info/index.php/food-model/209-articles.html?start=128 . Accessed: 24 July, 2017.

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